Wood fractionator



March 4, 1969 w H ETAL 3,430,873

WOOD FRACTIONA'IOR Filed Nov. 4, 1966 HAROLD F. WAH L ezvz m- BUCKHOR/V, BLORE, KLAROU/ST 8 SPAR/(MAN ATTORNEYS United States Patent 3,430,873 WOOD FRACTIONATOR Harold F. Wahl, Portland, and Harold Nipper-t, Boring,

Oreg., assignors to Rader Pneumatics Incorporated,

Portland, 0reg., a corporation of Oregon Filed Nov. 4, 1966, Ser. No. 592,019

U.S. Cl. 241-55 Int. Cl. B02c 13/04, 23/02; B07b 1/20 1 Claim ABSTRACT OF THE DISCLOSURE This invention relates to comminuting machines and, more particularly, to machines for fractionating and breaking large wood chips to a smaller size for making paper pulp.

Machines for fractionating wood chips commonly employ a plurality of rotatable hammers disposed within a casing for breaking up large wood chips which are fed into the casing through a hopper mounted on one side thereof. The hammers rotate very rapidly and impel the chips up against a cutter bar mounted on one side of the casing to cause the chips to break, the smaller pieces resulting therefrom then being able to pass through a screen located in the bottom of the casing. In machines as heretofore constructed, a very substantial back pressure develops in the inlet of the hopper to the casing which pressure tends to blow the incoming chips out through the hopper and interferes with the feeding in of chips.

A number of expedients have been tried in an attempt to eliminate this problem, but none has been fully satisfactory. Some machines have been provided with a cover on the top of the hopper to prevent the chips from being blown back out. Still other machines have been provided with a suction pump downstream of the screen in the casing, thereby to draw the chips therethrough against the back pressure created. Neither solution has been fully satisfactory and each, of course, has increased the cost of the machine.

It is thus the rimary object of the present invention to provide an improved machine for comminuting wood chips or the like, which machine will prevent chips from being blown back out through the hopper during the fractionating operation.

It is a further object of the present invention to provide such a machine that will be simpler and more economical to construct than those heretofore available.

These and other objects and advantages are achieved in the machine of our invention by providing a scroll within the casing of the machine and adjacent the inlet of the hopper thereto, the scroll being eccentric with respect to the path of the rotatable hammers of the machine. The scroll creates a low pressure area in the region of the inlet of the hopper to the casing, thereby not only to prevent blowback of material through the hopper while the hammers are rotating within the casing, but in addition, to facilitate feeding in of chips.

In the drawings,

FIG. 1 is a cross sectional view through a wood chip fractionator constructed in accordance with the present invention; and

Cir

FIG. 2 is a sectional view taken on line 22 of FIG. 1.

Referring to the drawings, the machine of the present invention consists of a suitable casing 10 into which wood chips or other similar materials may be introduced through a hopper 12 mounted on one side thereof. The casing 10 is mounted on a portable base such as channel beams 13. A plurality of hammers 14 spaced apart by washers 15, are pivotally supported in two sets, one on each of two diametrically positioned rods 16 which extend between a pair of disks 18. Additional rods 17 extend between the disks 18 to provide additional support. The disks 18 are keyed to a shaft 20 which is supported in bearings 22 and rotated by a motor 23 through a flexible coupling 24. The hammers 14 may be in the form of a plurality of thin steel plates of size, for example, 8 inches by 2 /2 inches and between inch and inch thick. When the machine is in operation, the shaft 20 and disks 18 rotate counterclockwise as indicated by the arrow in FIG. 1, and the centrifugal force maintains the hammers 14 in the radial position shown. A cutter bar 26 is attached by bolts 28 to a support block 30 mounted on one of the supporting channels 13. The cutter bar 26 is transversely adjustable by means of a set screw 34 so that inner edge 36 thereof is closely adjacent to the path of the hammers 14 as they rotate within the casing. A perforated bottom or screen 38 is provided within the casing so that the chips introduced through the hopper 12 and broken up by the action of the hammers 14 as they pass by the cutter bar 26, will pass through the casing into a receptacle (not shown). An access door 40 secured in position by pivotable lugs 42 is provided on the side of the casing opposite the hopper 12, and one or more suitable baffles 44, 46 are provided to maintain the chips in circulation Within the easing until they have been reduced to the desired size.

In the machine as thus described, a very substantial back pressure develops in the hopper 12 due to the high speed of rotation of the hammers 14, which back pressure tends to blow the chips back out of the hopper during the fractionating operation. We have found that it is possible to eliminate this problem entirely by providing a bafile or scroll 50 within the casing, above the inlet of the hopper 12 thereto and eccentric with respect to the path of the hammers 14 therein. The scroll 50 is preferably adjustably mounted. In the illustrated em bodiment, it is attached near one edge 51 to two lugs 52 mounted on either end of a rotatable shaft 54, thereby to be pivota'bly adjustable 'with respect to the casing 10. A set screw 56 in a bracket 58 mounted on top of the casing 10 above the scroll 50 may be provided to exert pressure on the edge 51 of the scroll above the lugs 52, thereby to make it possible to adjust the location of the other edge 60 of the scroll as desired. It should be noted that the edge 60 of the scroll terminates adjacent the infeed hopper 12 and in eflfect defines one side of the mouth thereof. The edge 60 is adjusted so that it is closely adjacent to the path of the hammers 14 as they rotate within the casing 10. Preferably, the scroll 50 is positioned so that a tangent drawn to its surface at the edge 60 will fall inside the inner edge 36 of the cutter bar 26. Thus, in its operating position the scroll 50 is positioned so that the edge 51 is remote from the path of the ends of the hammers 14 and the edge 60 is closely adjacent said path, so that the scroll may be said to converge towards the path in the direction of rotation of the hammers.

As the hammers 14 rotate, a high pressure area is produced immediately underneath the scroll 50 in the region of the numeral 62. The proximity of the edge 60 of the scroll to the path of the hammers 14 causes a high velocity air stream to be directed from beneath the scroll downwardly across the inlet of the hopper 12 to the casing which air stream develops a low-pressure area or partial vacuum inthe lower region 66 of the hopper. This action causes air to be pulled in through the hopper 12 rather than to be pumped out therethrough, which, of course, prevents any blowback of chips. The use of a cover on the hopper is thus unnecessary, as is any suction pump underneath the screen 38.

In the foregoing description, the invention has been described with reference to a certain particular preferred embodiment although it is to be understood that the specific details shown are merely illustrative and that the invention can be carried out in other ways without departing from the true spirit and scope of the following appended claim.

We claim:

1. A comminuting machine comprising a casing;

a plurality of hammers rotatably mounted within said casing;

a hopper mounted on one side of said casing;

a scroll provided within said casing above the inlet of said hopper thereto and eccentric with respect to the path of said hammers therein,

said scroll being pivotally mounted near one edge thereof, the other edge being closely adjacent 2 to said path of said hammers,

said scroll being constructed and arranged to create a low pressure area in the region of said inlet of said hopper to said casing, thereby to prevent blowback of material through said hopper and to facilitate feeding of said material into said casing; and means to adjust the position of said scroll with respect to said path of said hammers, said means comprising a bracket mounted on said casing above said scroll,

and at least one set screw passing through said bracket, said set screw being adapted to exert pressure on said one edge of said scroll, thereby to ad- DONALD R. SCHRAN, Primary Examiner.

FRANK T. YOST, Assistant Examiner.

U.S. Cl. X.R. 241-186 

